Imperial College London Assessment of Building Structures under Extreme Loading Bassam A. Izzuddin Department of Civil & Environmental Engineering

Buildings under Extreme Loading Modelling capabilities Progressive collapse Ongoing research 2 6 January 2011 GEMS 2011 Meeting

Modelling Capabilities Computational Structural Mechanics Group –2 academic staff (Izzuddin, Macorini) –2 RA’s, 8 PhD students – Focus on structures subject to extreme loading –Developments in computational mechanics –Applied structural engineering research –Novel modelling solutions for engineering practice Development of advanced program ADAPTIC 3 6 January 2011 GEMS 2011 Meeting

Advanced structural analysis program developed at Imperial College over past 20 years Blast, fire, earthquake and extreme static loading Steel, reinforced concrete and composite structures Whole building response: frame, slabs, walls, connections,… Geometric and material nonlinearity Robust and efficient solution procedures Modelling of large scale structures using HPC 4 6 January 2011 GEMS 2011 Meeting Modelling Capabilities ADAPTIC

Modelling Capabilities Simplified Methods Framework for progressive collapse assessment Steel beams subject to fire and blast loading Steel/composite beams with partial strength connections Membrane action in slabs Influence of material rate sensitivity 5 6 January 2011 GEMS 2011 Meeting

Modelling Capabilities Integrated Building Response Frame/slab substructure under sudden column loss 6 6 January 2011 GEMS 2011 Meeting

Modelling Capabilities Integrated Building Response Composite (ribbed) floor slab system under fire 7 6 January 2011 GEMS 2011 Meeting

Modelling Capabilities Connection Failure Detailed connection models with/without rate effect 8 6 January 2011 GEMS 2011 Meeting

Modelling Capabilities Slab failure Mechanics-based models for slabs subject to membrane action and reinforcement rupture 9 6 January 2011 GEMS 2011 Meeting

Modelling Capabilities Masonry Structures Multi-scale modelling of masonry structures under extreme loading 10 6 January 2011 GEMS 2011 Meeting FE modelling 3D Mesoscale model Material model Wpl1

Modelling Capabilities Partitioned Modelling on HPC Hierarchic partitioned approach for targeted model refinement and parallelisation on HPC 11 6 January 2011 GEMS 2011 Meeting

Progressive Collapse Assessment Design-Oriented Framework Robustness limit state –Prevention of collapse of upper floors –Stretching design envelope from strength to ductility limit Two stages of assessment –Nonlinear static response accounting for ductility limit –Simplified dynamic assessment 12 6 January 2011 GEMS 2011 Meeting

Progressive Collapse Assessment Design-Oriented Framework Maximum gravity load sustained under sudden column loss Multi-level framework Reduced model where deformation is concentrated Columns can resist re-distributed load Floors identical in components and loading Planar effects are neglected 13 6 January 2011 GEMS 2011 Meeting

Progressive Collapse Assessment Nonlinear Static Response Sudden column loss similar to sudden application of gravity load to structure without column –Maximum dynamic response can be approximated using amplified static loading ( d P ) 14 6 January 2011 GEMS 2011 Meeting Need models beyond conventional strength limit, including hardening, tensile catenary and compressive arching actions

Based on conservation of energy Work done by suddenly applied load equal to internal energy stored Leads to maximum dynamic displacement (also to load dynamic amplification) Definition of “pseudo-static” response Progressive Collapse Assessment Simplified Dynamic Approach 15 6 January 2011 GEMS 2011 Meeting

Ongoing Research Projects Robustness of composite buildings under localised fire (EU project: Liege, Imperial, Coimbra, …) Influence of material rate sensitivity on building robustness (Imperial, Trento) Keeping our structures standing and our people alive – The next 25 years (DHS project: Texas, Imperial, PEC, WPM) 16 6 January 2011 GEMS 2011 Meeting

Ongoing Research Projects DHS Project Testing of 3D floor systems to failure under column loss 17 6 January 2011 GEMS 2011 Meeting

Ongoing Research Projects DHS Project Sudden column loss vs blast damage –Column loss is an upper bound thus useful for design 18 6 January 2011 GEMS 2011 Meeting Sudden column loss

Ongoing Research Projects DHS Project Significance of uplift under external blast 19 6 January 2011 GEMS 2011 Meeting